Strain-Rate Dependence of the Martensitic Transformation Behavior in a 10 Pct Ni Multi-phase Steel Under Compression
Abstract not provided
Lambert, P. K.↗
SEARCH · Engineering Papers
Results for “Phase transformations”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Heterogeneous catalysis: Optimal performance at a phase boundary?
Most of the industrially used heterogeneous catalysts have been discovered by trial and error, and despite decades of experience, the discovery of new catalysts continues to be extremely challenging. The drive to uncover guiding principles in catalyst design is more present than ever. We share a series of observations indicating that optimal catalysts typically function at characteristic phase boundaries (e.g., abrupt changes in adsorbate coverage, catalyst structure, etc.) accessed in the reaction conditions. The catalyst exploits the associated instability—the desire to exist in multiple states simultaneously—as a driving force for chemical transformations. In other words, phase boundaries are good places to start the catalyst search, and indeed, we should focus on at least two phases at once rather than just one. Here, we substantiate this claim with several studies that combine statistical operando modeling and experiments. Transpiring from these observations is a hitherto unrecognized vector in catalyst discovery.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Citrate Controls Fe(II)-Catalyzed Transformation of Ferrihydrite by Complexation of the Labile Fe(III) Intermediate
Abstract not provided
Sheng, Anxu↗
Linear canonical transformations of coherent and squeezed states in the Wigner phase space. III - Two-mode states
It is shown that the basic symmetry of two-mode squeezed states is governed by the group SP(4) in the Wigner phase space which is locally isomorphic to the (3 + 2)-dimensional Lorentz group. This symmetry, in the Schroedinger picture, appears as Dirac's two-oscillator representation of O(3,2). It is shown that the SU(2) and SU(1,1) interferometers exhibit the symmetry of this higher-dimensional Lorentz group. The mathematics of two-mode squeezed states is shown to be applicable to other branches of physics including thermally excited states in statistical mechanics and relativistic extended hadrons in the quark model.
Han, D.↗
Optical recognition of statistical patterns
Optical implementation of the Fukunaga-Koontz transform (FKT) and the Least-Squares Linear Mapping Technique (LSLMT) is described. The FKT is a linear transformation which performs image feature extraction for a two-class image classification problem. The LSLMT performs a transform from large dimensional feature space to small dimensional decision space for separating multiple image classes by maximizing the interclass differences while minimizing the intraclass variations. The FKT and the LSLMT were optically implemented by utilizing a coded phase optical processor. The transform was used for classifying birds and fish. After the F-K basis functions were calculated, those most useful for classification were incorporated into a computer generated hologram. The output of the optical processor, consisting of the squared magnitude of the F-K coefficients, was detected by a T.V. camera, digitized, and fed into a micro-computer for classification. A simple linear classifier based on only two F-K coefficients was able to separate the images into two classes, indicating that the F-K transform had chosen good features. Two advantages of optically implementing the FKT and LSLMT are parallel and real time processing.
Lee, S. H.↗
Dark Energy Survey Year 3 results: Simulation-based cosmological inference with wavelet harmonics, scattering transforms, and moments of weak lensing mass maps. II. cosmological results
Here, we present a simulation-based cosmological analysis using a combination of Gaussian and non-Gaussian statistics of the weak lensing mass (convergence) maps from the first three years of the Dark Energy Survey. We implement the following: (1) second and third moments; (2) wavelet phase harmonics; (3) the scattering transform. Our analysis is fully based on simulations, spans a space of seven 𝑤 Cold Dark Matter (𝑤 CDM) cosmological parameters, and forward models the most relevant sources of systematics inherent in the data: masks, noise variations, clustering of the sources, intrinsic alignments, and shear and redshift calibration. We implement a neural network compression of the summary statistics, and we estimate the parameter posteriors using a simulation-based inference approach. Including and combining different non-Gaussian statistics is a powerful tool that strongly improves constraints over Gaussian statistics (in our case, the second moments); in particular, the figure of merit (𝑆 8 , Ω m ) is improved by 70% (Λ CDM) and 90% (𝑤 CDM). When all the summary statistics are combined, we achieve a 2% constraint on the amplitude of fluctuations parameter 𝑆 8 ≡ 𝜎 8 (Ω m /0.3) 0.5 , obtaining 𝑆 8 = 0.794 ±0.017 (Λ CDM) and 𝑆 8 = 0.817 ±0.021 (𝑤 CDM), and a ∼10% constraint on Ω m , obtaining Ω m =0.259 ±0.025 (Λ CDM) and Ω m = 0.273 ±0.029 (𝑤 CDM). In the context of the 𝑤 CDM scenario, these statistics also strengthen the constraints on the parameter 𝑤, obtaining 𝑤 <−0.72. The constraints from different statistics are shown to be internally consistent (with a 𝑝-value>0.1 for all combinations of statistics examined). We compare our results to other weak lensing results from the first three years of the Dark Energy Survey data, finding good consistency; we also compare with results from external datasets, such as planck constraints from the cosmic microwave background, finding statistical agreement, with discrepancies no greater than <2.2𝜎.
79 ASTRONOMY AND ASTROPHYSICS↗
In Situ Insights into Cathode Calcination for Predictive Synthesis: Kinetic Crystallization of LiNiO 2 from Hydroxides
Abstract Calcination is a solid‐state synthesis process widely deployed in battery cathode manufacturing. However, its inherent complexity associated with elusive intermediates hinders the predictive synthesis of high‐performance cathode materials. Here, correlative in situ X‐ray absorption/scattering spectroscopy is used to investigate the calcination of nickel‐based cathodes, focusing specifically on the archetypal LiNiO 2 from Ni(OH) 2 . Combining in situ observation with data‐driven analysis reveals concurrent lithiation and dehydration of Ni(OH) 2 and consequently, the low‐temperature crystallization of layered LiNiO 2 alongside lithiated rocksalts. Following early nucleation, LiNiO 2 undergoes sluggish crystallization and structural ordering while depleting rocksalts; ultimately, it turns into a structurally‐ordered layered phase upon full lithiation but remains small in size. Subsequent high‐temperature sintering induces rapid crystal growth, accompanied by undesired delithiation and structural degradation. These observations are further corroborated by mesoscale modeling, emphasizing that, even though calcination is thermally driven and favors transformation towards thermodynamically equilibrium phases, the actual phase propagation and crystallization can be kinetically tuned via lithiation, providing freedom for structural and morphological control during cathode calcination.
36 MATERIALS SCIENCE↗
Nucleation in the presence of long-range interactions
Unlike droplet nucleation near a liquid-gas critical point, the decay of metastable phases in crystalline materials is strongly affected by the presence of long-range forces. Field quench experiments performed on the ferroelectric barium titanate indicate that nucleation in this material is markedly different from that observed in liquids. In this paper, a theory for nucleation at a first-order phase transition in which the mediating forces are long range is presented. It is found that the long-range force induces cooperative nucleation and growth processes, and that this feedback mechanism produces a well-defined delay time with a sharp onset in the transformation to the stable phase. Closed-form expressions for the characteristic onset time and width of the transition are developed, in good agreement with numerical and experimental results.
Chandra, P.↗
New magnetic results from Allende C3/V/
Thermomagnetic analyses of Allende C3(V) suggest that magnetic phases contributing about 15% to saturation magnetization with transition temperatures not greater than 320 C, also contribute about 90% to natural remanence (NRM) and about 80% to the saturation isothermal remanence (SIRM). Phases carrying the dominating part of of the NRM are found to be intergrown, magnetically interacting, and thermally unstable, beginning at temperatures as low as 50 C. The ratio of the NRM/SIRM ranges from 0.004 to 0.006 for the bulk meteorite and from 0.0004 to 0.005 for chondrules of all sizes. The remanent coercive force behavior suggests coexisting magnetic phases with differing Curie points or with the low temperature transitions being due to transformation of a thermally metastable phase.
Wasilewski, P.↗
Formation and transformation of iron oxy-hydroxide precursor clusters to ferrihydrite
Iron (Fe) oxy-hydroxide minerals such as ferrihydrite (Fh) are ubiquitous in Earth-surface environments and important in biogeochemical element cycling. Recent research has suggested that their formation is preceded by the precipitation of ultrasmall (~1 nm) Keggin-like Fe oxy-hydroxide clusters. However, relatively little is understood about the structure of the precursor clusters and the impacts of pH and time on their growth and transformation to more stable phases. Here, we used a new method that involves mixed flow reactors (MFR) to synthesize these Fe oxy-hydroxide precursor clusters at pH 1.0, 1.5, 2.5, and 4.5. In situ and ex situ synchrotron scattering measurements and laboratory small-angle X-ray scattering (SAXS) were used to study the structure and size of Fe oxy-hydroxide clusters and their transformation products, respectively. Results show that with increasing pH, the particle size and structural order of samples increase, forming solids that resemble 2-line Fh at pH 4.5. The experimental data were compared with X-ray pair distribution functions (PDF) calculated for a range of Fe(III) oxyhydroxide clusters, including Fe 13 Keggin isomers computed previously using density functional theory (DFT), which yielded at best only partial agreement at short range (<5 Å). Aging of the clusters synthesized at pH 1.5 and 2.5 results in growth and transformation via Ostwald ripening to mixtures of goethite (Gt) and lepidocrocite (Lp). This process was inhibited by immediately reacting the early-formed clusters with phosphate (PO 4 3– ), suggesting that oxyanion surface complexes can stabilize the initial clusters by preventing growth and crystallization to more stable phases.
58 GEOSCIENCES↗
A low-temperature, one-step synthesis for monazite can transform monazite into a readily usable advanced nuclear waste form
It has been demonstrated that monazite-type materials are excellent candidates for nuclear waste forms, and hence, their facile synthesis is of great importance for the needed sequestration of existing nuclear waste. The synthesis of monazite, LaPO 4 , requires inconveniently high temperatures near 1000°C and generally involves the conversion of the presynthesized rhabdophane, LaPO 4 •nH 2 O, to the LaPO 4 monazite phase. During this structure transformation, the rhabdophane converts irreversibly to the thermodynamically stable monoclinic monazite structure. A low-temperature (185° to 260°C) mild hydrothermal acid-promoted synthesis of monazite is described that can both transform presynthesized rhabdophane or assemble reagents to the monoclinic monazite structure. The pH dependence of this reaction is detailed, and its applicability to the LnPO 4 (Ln = La, Ce, Pr, Nd, Sm-Gd), Ca 0.5 Th 0.5 PO 4 , and Sr 0.5 Th 0.5 PO 4 systems is discussed. The crystal growth of Ca 0.5 Th 0.5 PO 4 and Sr 0.5 Th 0.5 PO 4 is described, and their crystal structures were reported. In situ x-ray diffraction studies, performed as a function of temperature, provide insight into the structure transformation process.
Biogeochemistry↗
Vanishing dynamic strength measured in a transient high-pressure phase of tin
This work reports two independent experimental estimations of the dynamic strength of the body-centered tetragonal (bct) 𝛾 phase of tin, which occurs at pressures above about 9 GPa and transforms promptly back to the ambient 𝛽 phase upon pressure release. Measuring strength in such a transient high-pressure phase is challenging. One measurement used free-surface Richtmyer-Meshkov instabilities generated with gas gun impact. Another set of measurements used ramp-release loading in a pulsed-power facility. Strength estimations came from comparison to simulations using a comprehensive multiphase modeling framework that includes equation of state, shear moduli, and strength separately for each phase, and treats mixed-phase regions. Both experimental methods found the 𝛾-phase strength to be very low, within experimental uncertainty of zero. The existing literature on other materials, by contrast, almost universally reports higher strength in transient high-pressure phases compared with ambient phases. Recent Molecular-Dynamics simulations on tin in the literature showed almost zero deviatoric strength during a deformation-induced bct → bct transformation in which one of the 𝛾-phase 𝑎 axes “flips” to the 𝑐 axis. This reorientation currently provides the most plausible explanation for the low observed strength in 𝛾-phase tin.
36 MATERIALS SCIENCE↗
Generalized Quantum Signal Processing
Quantum signal processing (QSP) and quantum singular value transformation (QSVT) currently stand as the most efficient techniques for implementing functions of block-encoded matrices, a central task that lies at the heart of most prominent quantum algorithms. However, current QSP approaches face several challenges, such as the restrictions imposed on the family of achievable polynomials and the difficulty of calculating the required phase angles for specific transformations. In this paper, we present a generalized quantum signal processing (GQSP) approach, employing general SU(2) rotations as our signal-processing operators, rather than relying solely on rotations in a single basis. Our approach lifts all practical restrictions on the family of achievable transformations, with the sole remaining condition being that | P | ≤ 1 , a restriction necessary due to the unitary nature of quantum computation. Furthermore, GQSP provides a straightforward recursive formula for determining the rotation angles needed to construct the polynomials in cases where P and Q are known. In cases where only P is known, we provide an efficient optimization algorithm capable of identifying in under a minute of GPU time, a corresponding Q for polynomials of degree on the order of 10 7 . We further illustrate GQSP simplifies QSP-based strategies for Hamiltonian simulation, offer an optimal solution to the ϵ -approximate fractional query problem that requires O ( ( 1 / δ ) + log ( 1 / ϵ ) ) queries to perform where O ( 1 / δ ) is a proved lower bound, and introduces novel approaches for implementing bosonic operators. Moreover, we propose a novel framework for the implementation of normal matrices, demonstrating its applicability through synthesis of diagonal matrices, as well as the development of a new algorithm for convolution through synthesis of circulant matrices using only O ( d log N + log 2 N ) 1 and 2-qubit gates for a filter of lengths d . Published by the American Physical Society 2024
Motlagh, Danial↗
Atomic-Scale Observation of O1 Faulted Phase-Induced Deactivation of LiNiO 2 at High Voltage
LiNiO 2 and cobalt-free ultrahigh-Ni content cathodes suffer from rapid capacity loss and severe chemomechanical degradation, especially when operated at high voltages. Here, by cycling LiNiO 2 up to 4.7 V, we report the atomic-scale observation of O1 faulted phase-induced deactivation of LiNiO 2 . We found that although a thin layer of O3 phase forms on the particle surface by reversible O3 → O1 transformation during discharge, the bulk interior still maintains the O1 faulted phase, leading to rapid capacity loss of LiNiO 2 . Moreover, the atomic configuration of the O1/O3 interface is investigated comprehensively. We found that the misfit along the c axes of the O1 and O3 phases results in the formation of misfit dislocations, whereby cation mixing is promoted at dislocation cores. Further, a transition zone with continuous shear along the a-b plane is uncovered between the O1 and O3 phases for the first time. Besides, severe oxygen loss-induced pore formation and concurrent rock salt transformation are also identified.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Shock-induced phase transitions and stacking fault formation in additively manufactured eutectic high-entropy alloy Ni 40 Co 20 Fe 10 Cr 10 Al 18 W 2
Ni 40 Co 20 Fe 10 Cr 10 Al 18 W 2 additively manufactured using laser powder bed fusion (LPBF) is among the toughest as-built alloys reported and is a promising candidate for use in extreme environments. However, its behavior under multi-megabar pressure regimes remains unexplored. We used femtosecond in situ X-ray diffraction to investigate the shock response of LPBF Ni40Co20Fe10Cr10Al18W2 under laser-driven shock compression and release. Our results reveal that the initial dual-phase face-centered + body-centered structure transforms to a single face-centered phase over a wide pressure range of 84±10 to 277±55 GPa, followed by a transition to a single body-centered phase at 431±48 GPa. We establish the Hugoniot equation-of-state of LPBF Ni 40 Co 20 Fe 10 Cr 10 Al 18 W 2 and compare it to the benchmark alloy AlCoCrFeNi 2.1 , demonstrating the effects of W-doping and increased Al content. High stacking fault probabilities, close to those measured in Au and Ag, are observed upon compression. A portion of the stacking faults are annihilated upon release to ambient pressure.
36 MATERIALS SCIENCE↗
Performance evaluation of digital phase-locked loops for advanced deep space transponders
The performances of the digital phase-locked loops (DPLL's) for the advanced deep-space transponders (ADT's) are investigated. DPLL's considered in this article are derived from the analog phase-locked loop, which is currently employed by the NASA standard deep space transponder, using S-domain to Z-domain mapping techniques. Three mappings are used to develop digital approximations of the standard deep space analog phase-locked loop, namely the bilinear transformation (BT), impulse invariant transformation (IIT), and step invariant transformation (SIT) techniques. The performance in terms of the closed loop phase and magnitude responses, carrier tracking jitter, and response of the loop to the phase offset (the difference between in incoming phase and reference phase) is evaluated for each digital approximation. Theoretical results of the carrier tracking jitter for command-on and command-off cases are then validated by computer simulation. Both theoretical and computer simulation results show that at high sampling frequency, the DPLL's approximated by all three transformations have the same tracking jitter. However, at low sampling frequency, the digital approximation using BT outperforms the others. The minimum sampling frequency for adequate tracking performance is determined for each digital approximation of the analog loop. In addition, computer simulation shows that the DPLL developed by BT provides faster response to the phase offset than IIT and SIT.
Nguyen, T. M.↗
Automatic programming for critical applications
The important phases of a software life cycle include verification and maintenance. Usually, the execution performance is an expected requirement in a software development process. Unfortunately, the verification and the maintenance of programs are the time consuming and the frustrating aspects of software engineering. The verification cannot be waived for the programs used for critical applications such as, military, space, and nuclear plants. As a consequence, synthesis of programs from specifications, an alternative way of developing correct programs, is becoming popular. The definition, or what is understood by automatic programming, has been changed with our expectations. At present, the goal of automatic programming is the automation of programming process. Specifically, it means the application of artificial intelligence to software engineering in order to define techniques and create environments that help in the creation of high level programs. The automatic programming process may be divided into two phases: the problem acquisition phase and the program synthesis phase. In the problem acquisition phase, an informal specification of the problem is transformed into an unambiguous specification while in the program synthesis phase such a specification is further transformed into a concrete, executable program.
Loganantharaj, Raj L.↗
A note on the transformation to canonical /phase-variable/ form
Phase-variable canonical form for single input linear dynamical systems applied to linear control theory
CANONICAL PROBLEM↗